Light emitting diodes (LEDs) are display devices that use a semiconductor diode that emits light when charged with electricity. LEDs provide light in a wide array of electronic devices. For example, LEDs are used as on/off indicators in electronic devices, are used to provide LCD or keypad backlighting in handheld devices, such as personal digital assistants (PDAs) and cellular telephones, and are used for digital display readouts, such as electronic signs. Typically, LEDs are manufactured into an electronic chip (e.g., LED chips) that provide for easy integration into electronic devices.
Conventional LED chips employ surface mount technology (SMT) using a printed circuit board (PCB) as a base, with the LED die encapsulated into an epoxy resin. The encapsulating process typically used is transfer molding, which utilizes high temperature and pressure to melt the mold compound and force it into the mold cavity. Due to the use of SMT and transfer molding epoxy encapsulation, there are a number of problems inherent to the used of conventional LED chips.
Typical LED chips are subject to thermal breakdown as a result of the poor thermal dissipation properties of a typical PCB. Due to the poor heat dissipation of a typical PCB, an LED used in a high power or high brightness application, may fail. Therefore, typical LED chips are restricted to low power or brightness, or have short life spans.
Furthermore, an encapsulating process using transfer molding creates an epoxy molding over an LED on top of a PCB. An LED chip subjected to the elements is prone to delamination caused by moisture absorption. Delamination causes the epoxy molding to separate from the PCB, exposing the LED die to moisture, and eventually leading to failure. Due to the wide number of electronic devices using LEDs that are exposed to the elements, delamination is a wide problem. Moreover, transfer molding requires expensive tools, machines and materials, requiring a substantial investment that is not typically viable for small- and medium-scale production.